The pressure tester and method of testing of the present invention finds its primary use in connection with pressurized automobile engine cooling systems, particularly those systems including a pressure-type cap filler having a one-way vacuum valve. Although the invention is illustrated, and will be described, in that environment, it will be apparent to those skilled in the art that the tester and the method of testing disclosed herein may find suitable uses in other environments where it is desired to observe the pressure integrity of closed systems, the pressures under which pressure responsive valve systems will react to relieve pressure, and the effectiveness and proper calibration of the pressure responsive valves which may be employed in such systems.
The vast majority of internal combustion automobile and truck engines utilize a liquid cooling system to maintain the engine within an optimum range for operating efficiency, the liquid typically being water with certain additives. The cooling system of such internal combustion engines generally employs liquid flow paths that extend within the engine block where heat is transferred from the operating engine to the water, through a water pump which serves to circulate the liquid, and then through a radiator where heat transfer occurs between the liquid and the atmosphere. With the advent of higher horsepower in engines, the use of smaller radiators due to considerations of costs and styling limitations, and higher operating temperatures for the engines, a considerable amount of heat is developed which must be dissipated through a relatively small area represented by the radiator surface. As a consequence, the majority of these cooling systems operate under pressure. By pressurizing the system, the boiling point of the coolant is raised, resulting in less loss of coolant by evaporation with a proportional increase in cooling efficiency.
The amount of pressure developed in these cooling systems depends to a large extent upon the temperature of the coolant and the speed at which the engine is operated. Since the cooling system is designed to be a closed system, any minor leaks present anywhere in the flow path will reduce the efficiency of the system and can result in the excessive loss of coolant. As the coolant is lost through such leaks, the capability of the system to keep the engine temperature from rising above an optimum operating level is accordingly decreased, and if enough of the coolant is lost, overheating occurs with consequent damage to the engine. It is thus commonly observed that the cooling systems of internal combustion engines should be pressure tested periodically and on a regular basis in order to assess the integrity of the system and to detect the presence of leaks.
The pressurized cooling systems currently in use include a radiator having a filler neck formed to provide a mouth including a lip for securing engagement through a camming action with a filler cap to thereby form an outer closure seat around the mouth of the radiator. The typical cap designed for use with this system further includes a resiliently mounted valve element which forms an inner seal to the filler neck through cooperation with an inner seat within the neck. The valve element is under yielding spring pressure such that the inner seal will be broken within a rated pressure range. Ideally, the spring which presses the valve against the inner seat is calibrated to hold the valve in sealing engagement with the inner seat as long as the pressure within the system does not exceed a predetermined value, and then to yield whenever the pressure exceeds that value. Since the cooling efficiency of any such system is optimum when the system is operated under the pressure for which that system was designed, any weakening of the spring or malfunction of the valve which permits the premature escape of pressure will lower the efficiency of the system.
A coolant overflow vent and/or line is provided intermediate the outer and inner seals of the filler neck through which pressure relief occurs. In most vehicles which are equipped with coolant recovery systems, coolant passing through an overflow line is carried to a collection tank. When the engine cools, a one-way vacuum valve located internally of the radiator cap will open in response to the vacuum formed in the radiator, permitting coolant in the collection tank, or simply air, to flow back into the cooling system.
At the present time, there are on the market pressure testers that are designed to simply test the radiator and the radiator filler cap. Such devices typically comprise a small air pump and an associated pressure gauge that communicate with a cap-like fixture which is attachable to the radiator. For instance, when these devices are used to check the radiator, the fill cap is removed from the radiator and the cap-like fixture applied in its place. Pressure is then applied to the radiator, and thus to the entire coolant flow path, through use of the hand pump until the system is at its rated pressure level as measured by the gauge. If little or no pressure drop is thereafter observed, the radiator is presumed to be holding pressure properly. When these devices are used to check the radiator filler cap, the cap is connected directly to the device through the use of an adapter which serves to form a seal with the pressure valve of the filler cap similar to that which exists in the radiator filler neck. The adapter is then pressurized through use of the hand pump, and the gauge is observed for the tightness of the seal as well as for a measurement of when the pressure relief valve in the filler cap opens.
The prior art pressure tester presents a disadvantage in that at least two tests must be performed to test the integrity of the whole system. That is, the radiator and cap must be tested separately. The prior art tester does not provide for the simultaneous testing of the radiator cap and the remainder of the coolant system.
The prior art pressure tester is, in general, only operative to test the integrity of the inner seal of the radiator cap. It does not test the outer seal ordinarily formed with the lip and around the mouth of the filler neck. Additionally, testing with the prior art tester often requires several repeated tests of the cap to be made due to the often inexact seat formed between the valve of the cap, which will retain the seat impression of the filler neck, and the seat presented by the adapter of the pressure tester. This is particularly a problem when the radiator cap is new.
Also, the prior art tester requires that the cap be removed from the filler neck for test purposes. Consequently, a hot pressurized system must be allowed to cool so that the cap can be safely removed, or the system must be otherwise vented to reduce the pressure to a point where the filler cap can be removed. If venting of the hot system is done too quickly, this can result in an unnecessary as well as excessive loss of coolant.